Wideband impedance transformer composed of LTCC-based multi-layered CRLH architecture

In this paper, a 70.7 Ω quarter-length impedance transformer composed of a multi-layered composite right/left-handed transmission line is studied both theoretically and experimentally. In the theoretical analysis, fractional bandwidth of 49.3 % (f_c=6.90 GHz) is obtained for connecting circuits with different impedances, 50 Ω and 100 Ω. A prototype model containing two impedance transformers (impedance transition of 50Ω -100Ω -50Ω) is fabricated, and it is confirmed that the measured results show good agreement with the theory. The overall dimensions of the proposed impedance transformer are 1.43 mm × 1.59 mm × 0.95 mm, which size is competitive to the recent super-compact devices used in mobile phones and other wireless communication terminals.